Communications control system with a serial communications interface and a parallel communications interface

ABSTRACT

A communications control system is disclosed that includes a serial communications interface and a parallel communications interface for coupling a plurality of input/output modules with a control module. The serial communications interface is configured for connecting the plurality of input/output modules to the control module in parallel to transmit information between the plurality of input/output modules and the control module, and the parallel communications interface is configured for separately connecting the plurality of input/output modules to the control module to transmit information between the plurality of input/output modules and the control module, and to transmit information between individual ones of the plurality of input/output modules. The serial communications interface may comprise a multidrop bus, and the parallel communications interface may comprise a cross switch.

BACKGROUND

Industrial and process control systems include various types of controlequipment used in industrial production, such as Supervisory Control andData Acquisition (SCADA) systems, Distributed Control Systems (DCS), andother control equipment using, for example, Programmable LogicControllers (PLC). These control systems are typically used inindustries including electrical, water, oil, gas, and data. Usinginformation collected from remote stations in the field, automatedand/or operator-driven supervisory commands can be transmitted to fieldcontrol devices. These field devices control local operations, such asopening and closing valves and breakers, collecting data from sensorsystems, and monitoring a local environment for alarm conditions.

For example, SCADA systems typically use open-loop control with sitesthat may be widely separated geographically, using potentiallyunreliable or intermittent low-bandwidth/high-latency links. Thesesystems use Remote Terminal Units (RTUs) to send supervisory data to acontrol center. The RTUs may have a limited capacity for local controlswhen the master station is not available. DCS systems are generally usedfor real time data collection and control with high-bandwidth,low-latency data networks. PLCs typically provide Boolean logicoperations, timers, continuous control, and so on. However, asindustrial control systems evolve, new technologies are combiningaspects of these various types of control systems. For instance,Programmable Automation Controllers (PACs) can include aspects of SCADA,DCS, and PLCs.

SCADA systems can be used with industrial processes, includingmanufacturing, production, power generation, fabrication, and refining.They can also be used with infrastructure processes, including watertreatment and distribution, wastewater collection and treatment, oil andgas pipelines, electrical power transmission and distribution, windfarms, large communication systems, and so forth. Further, SCADA systemscan be used in facility processes for buildings, airports, ships, spacestations, and the like (e.g., to monitor and control Heating,Ventilation, and Air Conditioning (HVAC) equipment and energyconsumption). DCS systems are generally used in large campus industrialprocess plants, such as oil and gas, refining, chemical, pharmaceutical,food and beverage, water and wastewater, pulp and paper, utility power,mining, metals, and so forth. PLCs are typically used in industrialsectors and with critical infrastructures.

SUMMARY

A communications control system is disclosed. In one or moreimplementations, the communications control system includes a serialcommunications interface and a parallel communications interface forcoupling a plurality of input/output modules with a control module. Theserial communications interface is configured for connecting theplurality of input/output modules to the control module in parallel totransmit information between the plurality of input/output modules andthe control module, and the parallel communications interface isconfigured for separately connecting the plurality of input/outputmodules to the control module to transmit information between theplurality of input/output modules and the control module, and totransmit information between individual ones of the plurality ofinput/output modules. The serial communications interface may comprise amultidrop bus, and the parallel communications interface may comprise across switch.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

DRAWINGS

The Detailed Description is described with reference to the accompanyingfigures. The use of the same reference numbers in different instances inthe description and the figures may indicate similar or identical items.

FIG. 1 is a block diagram illustrating a communications control systemin accordance with example implementations of the present disclosure.

FIG. 2 is a circuit diagram illustrating a switch fabric for acommunications control system in accordance with example implementationsof the present disclosure.

FIG. 3 is an isometric view illustrating a communications control systemin accordance with example implementations of the present disclosure.

FIG. 4 is a side elevation view of the communications control systemillustrated in FIG. 3.

FIG. 5 is an end view of the communications control system illustratedin FIG. 3.

FIG. 6 is a partial cross-sectional end view of the communicationscontrol system illustrated in FIG. 3.

FIG. 7 is a cross-sectional view illustrating an input/output module forthe communications control system illustrated in FIG. 3.

FIG. 8 is an isometric view illustrating a support frame for thecommunications control system illustrated in FIG. 3.

FIG. 9 is a flow diagram illustrating a process for furnishingcommunication between multiple input/output modules and one or morecommunications/control modules in accordance with exampleimplementations of the present disclosure.

DETAILED DESCRIPTION

Overview

Process control systems typically use two types of busses: multidropbusses and parallel backplanes. A multidrop serial bus with a master andmultiple slave devices may be used for distributed control systems wherereliability is critical, such as safety-critical systems, and the like.However, as additional devices are connected to a multidrop serial bus,data transfer speeds between components within the system may slowconsiderably. A parallel backplane may be used where multiple devicesare connected in parallel, such as with programmable logic controllers.Parallel backplanes offer increased data transfer speeds compared tomultidrop serial busses. However, parallel backplanes do not offerredundancy for safety-critical systems.

Accordingly, communications control systems are described that include aswitch fabric having a serial communications interface (e.g., a serialor Multidrop Bus (MDB) with a master and multiple slaves) and a parallelcommunications interface (e.g., a parallel or point-to-point busimplemented using a cross switch, or the like). The serialcommunications interface and the parallel communications interface maybe used for connecting multiple Input/Output (I/O) modules tocommunications/control modules, and to one another.

In some implementations, the serial communications interface and theparallel communications interface may be formed on a single printedcircuit board. The serial communications interface may be configured forconnecting the plurality of input/output modules to a redundant controlmodule in parallel, and the parallel communications interface may beconfigured for separately connecting the plurality of input/outputmodules to the redundant control module. Information transmitted via theserial communications interface and/or the parallel communicationsinterface may be packetized. The control module may comprise a networkinterface for transmitting information collected from the plurality ofinput/output modules via a network, and so forth. Additionally, thecommunications control system may include a power module for supplyingelectrical power to at least one of the plurality of input/outputmodules.

A communications control system configured in accordance with thepresent disclosure may provide deterministic behavior (e.g., withrespect to data turnaround time) and reliability for critical systems,while still providing speed and scalability. The communications controlsystem may provide fault isolation, along with data turnaround timesthat do not increase as additional components are added to a system.Further, the communications control system may allow componentsconnected to the system to communicate directly with one another usingthe communications control system. Communications control systemsconfigured in this manner may be implemented in various systems that mayotherwise use a parallel backplane.

Example Implementations

FIGS. 1 through 8 illustrate an example communications control system100 in accordance with the present disclosure. In implementations, thecommunications control system 100 may be configured for use with processcontrol systems technology, and so forth. For example, thecommunications control system 100 may be used with a distributed controlsystem comprised of controller elements and subsystems, where thesubsystems are controlled by one or more controllers distributedthroughout the system. The communications control system 100 includes aswitch fabric 102 comprising a serial communications interface 104 and aparallel communications interface 106 for furnishing communications witha number of I/O modules 108.

The serial communications interface 104 may be implemented using a groupof connectors connected in parallel with one another. For example, theserial communications interface 104 may be implemented using a multidropbus 110, or the like. In implementations, the multidrop bus 110 may beused for configuration and diagnostic functions of the I/O modules 108.The parallel communications interface 106 allows multiple signals to betransmitted simultaneously over multiple dedicated high speed parallelcommunication channels. For instance, the parallel communicationsinterface 106 may be implemented using a cross switch 112, or the like.

In a particular implementation, as described in FIG. 2, the parallelcommunications interface 106 can be implemented using a four (4) wirefull duplex cross switch 112 with a dedicated connection to each I/Omodule 108. For example, the cross switch 112 can be implemented as aprogrammable cross switch connecting point-to-point busses and allowingtraffic between the I/O modules 108. The cross switch 112 may beconfigured by a master device, such as a communications/control module114. For example, a communications/control module 114 may configure oneor more sets of registers included in the cross switch 112 to controltraffic between the I/O modules 108. In implementations, acommunications/control module 114 may comprise a rule set dictating howthe I/O modules 106 are interconnected. For example, acommunications/control module 114 may comprise a set of registers, whereeach register defines the operation of a particular switch (e.g., withrespect to how packets are forwarded, and so forth). Thus, the crossswitch 112 may not necessarily auto-configure, instead implementing aconfiguration provided by a communications/control module 114. However,this configuration is provided by way of example only and is not meantto be restrictive of the present disclosure. Thus, in otherimplementations, the cross switch 112 may auto-configure.

The parallel communications interface 106 may be used for datacollection from the I/O modules 108. Further, because each I/O module108 has its own private bus to the master (e.g., communications/controlmodules 114), each I/O module 108 can communicate with the master at thesame time. Thus, the total response time for the communications controlsystem 100 may be limited to that of the slowest I/O module 108, insteadof the sum of all slave devices.

In implementations, the switch fabric 102, the serial communicationsinterface 104, and the parallel communications interface 106 may beimplemented in a single, monolithic circuit board 116. However, thisconfiguration is provided by way of example only and is not meant to berestrictive of the present disclosure. Thus, the serial communicationsinterface 104 and the parallel communications interface 106 may beimplemented using different arrangements of multiple components, such asmultiple discrete semiconductor devices for implementing the serialcommunications interface 104 and the parallel communications interface106 separately, and so forth.

The switch fabric 102 may be configured for connecting one or more I/Omodules 108 and transmitting data to and from the I/O modules 108. TheI/O modules 108 may comprise input modules, output modules, and/or inputand output modules. For instance, input modules can be used to receiveinformation from input instruments in the process or the field, whileoutput modules can be used to transmit instructions to outputinstruments in the field. For example, an I/O module 108 can beconnected to a process sensor, such as a sensor 118 for measuringpressure in piping for a gas plant, a refinery, and so forth. Inimplementations, the I/O modules 116 may be used to collect data andcontrol systems in applications including, but not necessarily limitedto: industrial processes, such as manufacturing, production, powergeneration, fabrication, and refining; infrastructure processes, such aswater treatment and distribution, wastewater collection and treatment,oil and gas pipelines, electrical power transmission and distribution,wind farms, and large communication systems; facility processes forbuildings, airports, ships, and space stations (e.g., to monitor andcontrol Heating, Ventilation, and Air Conditioning (HVAC) equipment andenergy consumption); large campus industrial process plants, such as oiland gas, refining, chemical, pharmaceutical, food and beverage, waterand wastewater, pulp and paper, utility power, mining, metals; and/orcritical infrastructures.

In implementations, the I/O module 108 may be configured to convertanalog data received from the sensor 118 to digital data (e.g., usingAnalog-to-Digital Converter (ADC) circuitry, and so forth). An I/Omodule 108 may also be connected to a motor 120 and configured tocontrol one or more operating characteristics of the motor 120, such asmotor speed, motor torque, and so forth. Further, the I/O module 108 maybe configured to convert digital data to analog data for transmission tothe motor 120 (e.g., using Digital-to-Analog (DAC) circuitry, and soforth). In implementations, one or more of the I/O modules 108 maycomprise a communications module configured for communicating via acommunications sub-bus, such as an Ethernet bus, an H1 field bus, aProcess Field Bus (PROFIBUS), a Highway Addressable Remote Transducer(HART) bus, a Modbus, and so forth. Further, two or more of the I/Omodules 108 can be used to provide fault tolerant and redundantconnections for a communications sub-bus.

Each I/O module 108 may be provided with a unique identifier (ID) fordistinguishing one I/O module 108 from another I/O module 108. Inimplementations, an I/O module 108 may be identified by its ID when itis connected to the communications control system 100. Multiple I/Omodules 108 can be used with the communications control system 100 toprovide redundancy. For example, two or more I/O modules 108 can beconnected to the sensor 118 and/or the motor 120, as described inFIG. 1. Each I/O module 108 can include one or more ports 122 furnishinga physical connection to hardware and circuitry included with the I/Omodule 108, such as a Printed Circuit Board (PCB) 124, and so forth.

One or more of the I/O modules 108 may include an interface forconnecting to other networks, including but not necessarily limited to:a wide-area cellular telephone network, such as a 3G cellular network, a4G cellular network, or a Global System for Mobile communications (GSM)network; a wireless computer communications network, such as a Wi-Finetwork (e.g., a Wireless LAN (WLAN) operated using IEEE 802.11 networkstandards); a Personal Area Network (PAN) (e.g., a Wireless PAN (WPAN)operated using IEEE 802.15 network standards); a Wide Area Network(WAN); an intranet; an extranet; an internet; the Internet; and so on.Further, one or more of the I/O modules 108 may include a connection forconnecting an I/O module 108 to a computer bus, and so forth.

The switch fabric 102 may be coupled with one or morecommunications/control modules 114 for monitoring and controlling theI/O modules 108, and for connecting the I/O modules 108 together. Thecommunications/control module(s) 114 may be used to configure the crossswitch 112. For example, a communications/control module 114 may updatea routing table when an I/O module 108 is connected to thecommunications control system 100 based upon a unique ID for the I/Omodule 108. Further, when multiple redundant I/O modules 108 are used,each communications/control module 114 can implement mirroring ofinformational databases regarding the I/O modules 108 and update them asdata is received from and/or transmitted to the I/O modules 108. In someimplementations, two or more communications/control modules 114 may beused to provide redundancy.

Data transmitted using the switch fabric 102 may be packetized, i.e.,discrete portions of the data may be converted into data packetscomprising the data portions along with network control information, andso forth. The communications control system 100 may use one or moreprotocols for data transmission, including a bit-oriented synchronousdata link layer protocol such as High-Level Data Link Control (HDLC). Ina specific instance, the communications control system 100 may implementHDLC according to an International Organization for Standardization(ISO) 13239 standard, or the like. Further, two or morecommunications/control modules 114 can be used to implement redundantHDLC. However, it should be noted that HDLC is provided by way ofexample only and is not meant to be restrictive of the presentdisclosure. Thus, the communications control system 100 may use othervarious communications protocols in accordance with the presentdisclosure.

One or more of the communications/control modules 114 may be configuredfor exchanging information with components used for monitoring and/orcontrolling the instrumentation connected to the switch fabric 102 viathe I/O modules 108, such as one or more control loop feedbackmechanisms/controllers 126. In implementations, a controller 126 can beconfigured as a microcontroller/Programmable Logic Controller (PLC), aProportional-Integral-Derivative (PID) controller, and so forth. One ormore of the communications/control modules 114 may include a networkinterface 128 for connecting the communications control system 100 to acontroller 126 via a network 130. In implementations, the networkinterface 128 may be configured as a Gigabit Ethernet interface forconnecting the switch fabric 102 to a Local Area Network (LAN). Further,two or more communications/control modules 114 can be used to implementredundant Gigabit Ethernet. However, it should be noted that GigabitEthernet is provided by way of example only and is not meant to berestrictive of the present disclosure. Thus, the network interface 128may be configured for connecting the communications control system 100to other various networks, including but not necessarily limited to: awide-area cellular telephone network, such as a 3G cellular network, a4G cellular network, or a Global System for Mobile communications (GSM)network; a wireless computer communications network, such as a Wi-Finetwork (e.g., a Wireless LAN (WLAN) operated using IEEE 802.11 networkstandards); a Personal Area Network (PAN) (e.g., a Wireless PAN (WPAN)operated using IEEE 802.15 network standards); a Wide Area Network(WAN); an intranet; an extranet; an internet; the Internet; and so on.Additionally, the network interface 128 may be implemented usingcomputer bus. For example, the network interface 128 can include aPeripheral Component Interconnect (PCI) card interface, such as a MiniPCI interface, and so forth. Further, the network 130 may be configuredto include a single network or multiple networks across different accesspoints.

The communications control system 100 may include one or more powermodules 132 for supplying electrical power to field devices via the I/Omodules 108. One or more of the power modules 132 may include anAC-to-DC (AC/DC) converter for converting Alternating Current (AC)(e.g., as supplied by AC mains, and so forth) to Direct Current (DC) fortransmission to a field device, such as the motor 120 (e.g., in animplementation where the motor 120 comprises a DC motor). Two or morepower modules 132 can be used to provide redundancy. For example, asshown in FIG. 1, two power modules 132 can be connected to each of theI/O modules 108 using a separate power backplane 134 for each powermodule 132.

The communications control system 100 may be implemented using a supportframe 136. The support frame 136 may be used to support and/orinterconnect the communications/control module(s) 114, the powermodule(s) 132, the switch fabric 102, the power backplane(s) 134, and/orthe I/O modules 108. The circuit board 116 may be mounted to the supportframe 136 using a fastener such as, for example, double sided tape,adhesive, or mechanical fasteners (e.g., screws, bolts, etc.). Thesupport frame 136 may include slots 138 to provide registration for theI/O modules 108, such as for aligning connectors of the I/O modules 108with connectors included with the circuit board 116 and/or connectors ofa power backplane 134. For example, an I/O module 108 may includeconnectors 140 having tabs/posts 142 for inserting into slots 138 andproviding alignment of the I/O module 108 with respect to the circuitboard 116. In implementations, one or more of the connectors 140 may beconstructed from a thermally conductive material (e.g., metal) connectedto a thermal plane of PCB 124 to conduct heat generated by components ofthe PCB 124 away from the PCB 124 and to the support frame 136, whichitself may be constructed of a thermally conductive material (e.g.,metal). Further, the communications control system 100 may associate aunique physical ID with each physical slot 138 to uniquely identify eachI/O module 108 coupled with a particular slot 138. For example, the IDof a particular slot 138 can be associated with an I/O module 108coupled with the slot 138 and/or a second ID uniquely associated withthe I/O module 108. Further, the ID of a particular I/O module 108 canbe used as the ID for a slot 138 when the I/O module 108 is coupled withthe slot 138. The support frame 136 can be constructed for cabinetmounting, rack mounting, wall mounting, and so forth.

It should be noted that while the communications control system 100 isdescribed in the accompanying figures as including one switch fabric102, more than one switch fabric 102 may be provided with communicationscontrol system 100. For example, two or more switch fabrics 102 may beused with the communications control system 100 (e.g., to providephysical separation between redundant switch fabrics 102, and so forth).Each one of the switch fabrics 102 may be provided with its own supportframe 136. Further, while both the serial communications interface 104and the parallel communications interface 106 are described as includedin a single switch fabric 102, it will be appreciated that physicallyseparate switch fabrics may be provided, where one switch fabricincludes the serial communications interface 104, and another switchfabric includes the parallel communications interface 106.

Example Process

Referring now to FIG. 9, example techniques for furnishing communicationbetween multiple input/output devices and one or morecommunications/control modules using a communications control systemthat includes a serial communications interface and a parallelcommunications interface for coupling a plurality of input/outputmodules with a control module are described.

FIG. 9 depicts a process 900, in an example implementation, forfurnishing a communications control system, such as the communicationscontrol system 100 illustrated in FIGS. 1 through 8 and described above.In the process 900 illustrated, input/output modules are coupled with acontrol module (Block 910). For example, with reference to FIGS. 1through 8, the switch fabric 102 may be configured for connecting theI/O modules 108 to the communications/control modules 114, andtransmitting data to and from the I/O modules 108. The input/outputmodules are connected to the control module in parallel for transmittinginformation between the input/output modules and the control module(Block 920). In one or more implementations, the input/output modulescan be connected to the control module using a multidrop bus (Block922). For instance, with continuing reference to FIGS. 1 through 8, theserial communications interface 104 of the switch fabric 102 may beimplemented using a multidrop bus 110. The input/output modules areseparately connected to the control module for transmitting informationbetween the input/output modules and the control module, and fortransmitting information between individual ones of the input/outputmodules (Block 930). In one or more implementations, the input/outputmodules can be separately connected to the control module using a crossswitch (Block 932). For example, with continuing reference to FIGS. 1through 8, the parallel communications interface 106 of the switchfabric 102 may be implemented using a cross switch 112 comprising a four(4) wire full duplex system with a dedicated connection to each I/Omodule 108.

In some implementations, the input/output modules are coupled with aredundant control module (Block 940). The input/output modules can beconnected to the redundant control module in parallel (Block 950). Theinput/output devices can also be separately connected to the redundantcontrol module (Block 960). For instance, with continuing reference toFIGS. 1 through 8, two or more communications/control modules 114 can beused to implement a redundant HDLC data link layer protocol. It shouldbe noted that connecting the input/output modules to one redundantcontrol module is provided by way of example only and is not meant to berestrictive of the present disclosure. Thus, the input/output modulesmay be connected to more than one redundant control module in paralleland/or separately.

In some implementations, the control module can be coupled with anetwork for transmitting information collected from the input/outputmodules via the network (Block 970). For example, with continuingreference to FIGS. 1 through 8, one or more of thecommunications/control modules 114 may include a network interface 128for connecting the communications control system 100 to a controller 126via a network 130. The input/output modules can also be coupled with apower module for supplying electrical power to the input/output modules(Block 980). For instance, with continuing reference to FIGS. 1 through8, one or more power modules 132 may be included with the communicationscontrol system 100 for supplying electrical power to field devices viathe I/O modules 108.

CONCLUSION

Although the subject matter has been described in language specific tostructural features and/or process operations, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A communications control system comprising: a control module; aplurality of input/output modules coupled with the control module; aserial communications interface configured for connecting the pluralityof input/output modules to the control module in parallel, the serialcommunications interface configured for transmitting information betweenthe plurality of input/output modules and the control module; and aparallel communications interface configured for separately connectingthe plurality of input/output modules to the control module, theparallel communications interface configured for transmittinginformation between the plurality of input/output modules and thecontrol module, and transmitting information between individual ones ofthe plurality of input/output modules, each one of the plurality ofinput/output modules identifying itself to the control module using aunique identification upon connecting to the control module, the controlmodule maintaining a routing table with the unique identification foreach input/output module connected to the control module, the uniqueidentification comprising at least one of an identifier associated withthe input/output module or an identifier associated with a slot thatprovides registration for the input/output module.
 2. The communicationscontrol system as recited in claim 1, wherein the serial communicationsinterface comprises a multidrop bus.
 3. The communications controlsystem as recited in claim 1, wherein the parallel communicationsinterface comprises a cross switch.
 4. (canceled)
 5. The communicationscontrol system as recited in claim 1, wherein the serial communicationsinterface is configured for connecting the plurality of input/outputmodules to a redundant control module in parallel, and the parallelcommunications interface is configured for separately connecting theplurality of input/output modules to the redundant control module. 6.The communications control system as recited in claim 1, whereininformation transmitted via at least one of the serial communicationsinterface or the parallel communications interface is packetized.
 7. Thecommunications control system as recited in claim 1, wherein the controlmodule comprises a network interface for transmitting informationcollected from the plurality of input/output modules via a network. 8.The communications control system as recited in claim 1, furthercomprising a power module for supplying electrical power to at least oneof the plurality of input/output modules.
 9. A process comprising:coupling a plurality of input/output modules with a control module;connecting the plurality of input/output modules to the control modulein parallel for transmitting information between the plurality ofinput/output modules and the control module; separately connecting theplurality of input/output modules to the control module for transmittinginformation between the plurality of input/output modules and thecontrol module, and transmitting information between individual ones ofthe plurality of input/output modules; establishing a routing table;identifying each one of the plurality of input/output modules to thecontrol module using a unique identification upon connecting to thecontrol module; and maintaining the routing table with the uniqueidentification for each input/output module connected to the controlmodule, the unique identification comprising at least one of anidentifier associated with the input/output module or an identifierassociated with a slot that provides registration for the input/outputmodule.
 10. The process as recited in claim 9, wherein connecting theplurality of input/output modules to the control module in parallelcomprises connecting the plurality of input/output modules to thecontrol module using a multidrop bus.
 11. The process as recited inclaim 9, wherein separately connecting the plurality of input/outputmodules to the control module comprises separately connecting theplurality of input/output modules to the control module using a crossswitch.
 12. (canceled)
 13. The process as recited in claim 9, furthercomprising: coupling the plurality of input/output modules with aredundant control module; connecting the plurality of input/outputmodules to the redundant control module in parallel; and separatelyconnecting the plurality of input/output modules to the redundantcontrol module.
 14. The process as recited in claim 9, wherein at leastone of transmitting information between the plurality of input/outputmodules and the control module or transmitting information betweenindividual ones of the plurality of input/output modules comprisespacketizing the transmitted information.
 15. The process as recited inclaim 9, further comprising coupling the control module with a networkfor transmitting information collected from the plurality ofinput/output modules via the network.
 16. The process as recited inclaim 9, further comprising coupling at least one of the plurality ofinput/output modules with a power module for supplying electrical powerto the at least one of the plurality of input/output modules.
 17. Acommunications control system comprising: a first control module; asecond control module; a plurality of input/output modules coupled withthe ft control module and the second control module; a multidrop busconfigured for connecting the plurality of input/output modules to thefirst control module and the second control module in parallel, themultidrop bus configured for transmitting information between theplurality of input/output modules and the first control module and thesecond control module; and a cross switch configured for separatelyconnecting the plurality of input/output modules to the first controlmodule and the second control module, the cross switch configured fortransmitting information between the plurality of input/output modulesand the first control module and the second control module, andtransmitting information between individual ones of the plurality ofinput/output modules, the first control module and the second controlmodule each maintaining a mirrored routing table.
 18. The communicationscontrol system as recited in claim 17, wherein the control module isconfigured to assign each input/output module a unique identifierassociated with a physical location where the input/output module isphysically connected to the control module.
 19. (canceled)
 20. Thecommunications control system as recited in claim 17, whereininformation transmitted via at least one of the multidrop bus or thecross switch is packetized.